I. Field of the Invention
This invention relates generally to a surgical instrument used during a vascular interventional procedure, and more particularly to an instrument for accurately measuring the depth below the skin surface of the blood vessel through which the vascular catheter is to be passed.
II. Discussion of the Prior Art
In a typical interventional procedure, such as the placement of a vascular catheter, the so-called Seldinger procedure is used to gain access to a blood vessel. More particularly, a needle trocar is passed through the skin to puncture an opening through the wall of an artery. Next, a dilator may be passed over the trocar to slightly enlarge the diameter of the puncture wound so that it can accommodate a tubular introducer. Once the introducer is in place, an elongated, flexible guidewire may be passed through the introducer into the blood vessel. An interventional device may then be advanced over the guidewire and through the vascular system.
Once the procedure in question has been concluded and the interventional device has been withdrawn, any guide catheter, the guidewire and the introducer must also be removed. As is explained in a co-pending U.S. Pat. application of Makower et. al. Ser. No. 07/912,921, filed Jul. 13, 1992, and entitled "HEMOSTATIC IMPLANT INTRODUCER", a difficulty often arises in stemming the flow of blood through the entry wound. When only manual pressure is relied upon to stem the blood flow, considerable time is required on the part of surgical personnel to maintain the pressure until clotting has taken place. The device described in the aforereferenced Makower et. al. application has been especially designed to more rapidly effect hemostasis by providing a means for injecting a mass of hemostatic material (collagen) as a plug into the puncture wound. That device is intended to position the collagen plug beneath the skin and directly in contact with the exterior wall of the punctured blood vessel, but without introducing any of the collagen plug material through that puncture site. To accomplish this end, it is important that the depth of the punctured blood vessel beneath the skin surface be accurately gauged so that the surgeon can accurately place the barrel of the puncture sealing device (PSD) into the wound only to that desired depth, thus assuring that the plug will not be made to enter the blood vessel where it could act as a thrombogenic site.